Get slim without losing weight

Patient : Hi
I do not weigh so much, I am underweight. But still I want to get thinner stomach and thighs. Are there some exercise I can do or some food I can eat to get a flat stomach or slimer thighs without losing weight?
Emmy

(*)
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.